This invention relates generally to the field of magnetic data storage devices, and more particularly, but not by way of limitation, to improving mechanical shock performance through the use of rings of high friction material in disc support members used to mount a rotatable disc to a spindle motor.
Disc drives are used as primary data storage devices in modem computer systems and networks. A typical disc drive comprises one or more rigid magnetic storage discs which are journaled about a spindle motor for rotation at a constant high speed. An array of read/write transducing heads are provided to transfer data between tracks of the discs and a host computer in which the disc drive is mounted. The heads are mounted to a rotary actuator assembly and are controllably positioned adjacent the tracks by a closed loop servo system.
As disc drives become smaller and store greater amounts of data, reliability problems can increasingly arise from the application of mechanical shocks to the drives. Such shocks, if sufficiently severe, can cause a shift in the discs relative to the rotatable hubs of the spindle motor supporting the discs, inducing eccentricities in the tracks sufficient to prevent the drives from retrieving previously stored data.
Increasing the clamping force used to secure the discs to the hub can increase resistance to mechanical shocks, but too much clamping force can undesirably induce warping of the discs. Thus, various prior art approaches to reducing disc slip have included using xe2x80x9cteethxe2x80x9d to interlock the discs and adjacent disc spacers as taught by U.S. Pat. No. 5,596,462 to Smith and U.S. Pat. No. 5,875,171 to Albrecht et al.; using a coating of higher friction elastomeric material between each adjacent disc and spacer as taught by U.S. Pat. Nos. 4,945,432 and 5,031,062; and using compressible o-rings in grooves formed in spacers as taught by U.S. Pat. Nos. 5,272,581 and 5,636,084.
While operable, there remains a continued need for improvements in the art to increase the resistance to disc slip as a result of mechanical shocks.
The present invention is directed to an apparatus for improving resistance of a disc drive disc stack to radially directed mechanical shocks.
In accordance with preferred embodiments, a disc drive includes a spindle motor hub which is configured for rotation about a central axis and has a circumferentially extending outer hub surface. A disc circumferentially extends about the outer hub surface and has top and bottom disc surfaces each extending along planes substantially normal to the central axis, with the disc having a disc coefficient of friction.
Opposing first and second disc support members (such as a disc clamp, disc spacers or a hub flange) circumferentially extend about the outer hub surface and cooperate to apply a clamping force to the disc to secure the disc relative to the spindle motor hub. The first and second disc support members each comprise a radially extending support member surface immediately adjacent the disc along a plane substantially normal to the central axis and a circumferentially extending ring having a contact surface that axially extends from the radially extending support member surface toward the disc. Each ring has a coefficient of friction greater than the disc coefficient of friction.
Each support member further comprises a circumferentially extending node that axially extends from the radially extending support surface toward the disc. The clamping force applied to the top and bottom disc surfaces is localized by the contact surfaces of the rings and the circumferentially extending node so that respective gaps are formed between the top and bottom disc surfaces and the radially extending support member surfaces. This reduces the likelihood of disc coning or warping.
By increasing the coefficient of friction at the boundaries securing the discs, smaller normal clamping forces can be used to achieve the same levels of radial shock resistance. Conversely, the same levels of normal clamping force can be applied to achieve greater levels of radial shock resistance. Moreover, the rings improve the mechanical coupling of the discs to the spindle hub, thereby reducing disc ringing in response to axially and radially directed mechanical shocks.
These and various other features and advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.